Nonreciprocal solid state waveguide and devices utilizing same



June 1%? MINORU TODA 3,327,247

NONRECIPROCAL SOLID STATE WAVEGUIDE AND DEVICES UTILIZING SAME Filed July 14, 1965 2 Sheets-Sheet 1 you/0 A UPUGZ/V A COOL/N6 5/4779 i Whea- IN VE N TOR. W/Mwu 750,4

Alta/wry Z2) kMdioM/i 5/64/44 5mm 20, 39%? MINORU TODA 393279247 NONRECIPROCAL SOLID STATE WAVEGUIDE AND DEVICES UTILIZING SAME Filed July 14, 1965 2 Sheets-Sheet 2 aw/W;

1 N VE N TOR. W/Wfil/ 70m wweg 91m:

United States Patent O 3,327,247 NONRECIPROCAL SOLID STATE WAVEGUIDE AND DEVICES UTILIZING SAME Minoru Toda, Tokyo, .lapan, assignor to Radio (Iorporation of America, a corporation of Delaware Fiied July 14, 1965, Ser. No. 471,921 19 Claims. (Cl. 333l.1)

This invention relates to a solid state waveguide and more particularly to the application of this waveguide to such devices as isolators, modulators, circulators, phase shifters, switches, and the like.

It is an object of this invention to provide an improved nonreciprocal solid state waveguide through which microwave energy can be propagated.

It is a further object of this invention to employ the nonreciprocal properties exhibited by the waveguide in switches, isolators, circulators, modulators and similar devices.

Another object of this invention is to permit by the use of an improved structure a greater variety of modes of propagation of microwave energy through a solid state waveguide.

It is still another object of this invention to provide an improved solid state waveguide having a much higher frequency limitation than has heretofore been possible.

Certain solid state materials such as ferrites, semiconductors, and semimetals are anisotropic in the presence of a magnetic field. Thus, microwave energy is attenuated if propagated through such materials in one direction. However, if propagated in another direction, the energy suffers little attenuation. This anisotropic or nonreciprocal property can be employed in such devices as isolators, circulators, and the like.

In accordance with the present invention, microwave energy is propagated through a waveguide made of a solid state material. A magnetic field is applied in a direction substantially parallel to and coincident with a surface of the solid state material. Microwave energy is coupled into the solid state material so that it can propagate parallel to the surface of the material and perpendicular to the direction of the magnetic field. It has been found that microwave energy will propagate through such material in the presence of a transverse magnetic field if the surface of the solid state material is coated with a conductive substance.

Thus, in one embodiment of the invention, a rectangular solid state waveguide has a metal coat on at least one surface. Microwave energy in the TE mode is applied in a given direction to and through the solid state waveguide with its electric field component perpendicular to the coated surface. A magnetic field is applied perpendicularly to the direction of the microwave energy and coincident with the metal coated surface. The microwave energy can be made to propagate within the solid state material and along the metal coated surface of the solid state waveguide with little attenuation. The phenomenon of propagating a signal along a metal coated surface Within solid state material as provided by the present invention can be employed in such devices as circulators, isolators, phase shifters, switches, modulators, and the like.

The novel features of the present invention, both as to its method and organization as well as additional objects and advantages thereof, will be understood more fully from the following detailed description when read in connection with the accompanying drawing in which similar reference characters designate similar parts throughout and in which:

' IG. 1 is a partially sectioned, perspective view of a solid state waveguide isolator constructed in accordance with the invention;

FIG. 2 is a sectioned view of a phase shifter constructed in accordance with the invention;

FIG. 3 is a sectioned view of a duplexer constructed in accordance with the invention;

FIG. 4 is a sectioned view of a circulator constructed in accordance with the invention; and

FIG. 5 is a schematic view of a waveguide switch and modulator constructed in accordance with the invention.

A waveguide isolator absorbs energy in one direction and permits propagation in the reverse direction. An example of a solid state waveguide isolator employing the inventive structure is shown in FIG. 1.

A solid state waveguide 8 is aifixed between two hollow waveguides 10 and 12 such that microwave energy (the source of which is not shown) propagated into the first hollow waveguide 10, proceeds axially into the solid state waveguide 8 and into the second hollow waveguide 12. The solid state waveguide 8 comprises a solid state material 14, which can be a semiconductor or semimetal, having a rectangular shape. Two parallel side surfaces 16 and 18 and an adjacent top surface 20 are covered with a sheet or a coating of a conductive substance 22, for example, copper. So that microwave energy is efliciently coupled to the solid state waveguide 8, two parallel exposed end surfaces 24 and 26 of the waveguide, not covered by metal, are inserted a short distance into the hollow waveguides 10 and 12, respectively.

The direction of propagation of microwave energy from the first hollow waveguide 10, through the solid state waveguide 8 and into the second hollow waveguide 12 can be indicated by a vector arrow 28 drawn on the x-axis of a coordinate system 30. A direct current (DC) magnetic field indicated by an arrow H is directed by suitable means not shown coincident with the waveguide '3, parallel to the top surface 20 and perpendicularly to the side surfaces 16 and 18 of the solid state Waveguide 8. The magnetic field is thus directed transverse to the direction of propagation of the microwave energy through the waveguide 8. Although the means for applying the magnetic field, which can be accomplished by any suitable known technique, are not shown in FIG. 1, its direction is indicated on the coordinate system 30 as a vector 32 on the z-axis. The RF electric field of the microwave energ is substantially perpendicular to the DC. magnetic field and is represented by a vector 34 on the y-axis of the coordinate system 30. The non-metallized, bottom surface 36 of the waveguide 8 can be covered wit-h an ergy absorbing substance 38, for example, silicone grease-carbon powder compound.

In describing the operation of a solid state waveguide of the type shown in FIG. 1 reference will be made, by way of example, to various dimensions and quantities. The solid state waveguide 8 has, for example, end surfaces 24 and 26 of approximately 2 millimeters by 2 millimeters. The distance or length betweeii the two end surfaces 24 and 26 is 5.5 millimeters. Thus, the top surface 20 and the parallel uncoated bottom surface 36 have dimensions of 2 millhneters by 5.5 millimeters. Each of the end sufaces 24- and 26 is inserted a distance of .75 millimeter into the hollow waveguides 10 and i2, respectively.

In order to prevent unnecessary loss of microwave power, the coat 22 of conductive substance, which can be a metal such as copper, on the solid state waveguide 8 and the metal walls of the hollow waveguides it) and 12 are of a thickness greater than the skin depth penetration of the microwave energy. By way of example, the metal should be thick enough to retain the energy of a 24 gc. microwave signal. The two parallel side surfaces 16 and 18 are covered with the metal coating 22 so as to prevent the unnecessary radiation of energy. The metal coating on the top suface 20' is necessary for both the prevention of radiation and the propagation of the microwave energy. Spaces between the hollow waveguides 1th and 12 and the end surfaces 24 and 26 can be sealed with a conductive substance such as silicon grease and brass powder.

The solid state substance 14 employed in a solid state waveguide 8 can be of any semimetal or semiconductor. For purposes of this example, the solid state substance 14- is n-type indium antimonide (n-InSb) having an electron density of 10 mi (in mks. units). Although it is believed possible to propagate a signal through the solid state waveguide 8 at room temperatures, for purposes of this example, the entire structure is immersed in a cooling bath such as a liquid nitrogen (shown in FIG. 1 in dotted lines 39) which maintains the solid state Waveguide 8 at a temperature of 77 K.

The microwave energy, at a frequency of 24 gc., for example, is supplied to the first hollow waveguide 18 in a TE mode. The energy conforms to this mode due to the configuration of the solid state and hollow waveguides 8, 10, and 12. The wave is propagated in a direction indicated by the vector 28 along the x-axis. The signal Passes through the hollow waveguide 10, into the end surface 24 of the solid state waveguide 8, along the length of the solid state waveguide 8, out the other end surface 26, and

into the second hollow waveguide 12. The electric field of r the microwave energy is perpendicular to the top surface 20 of the solid state waveguide 8, as indicated by the vector 34.

In the example given, a magnetic field in excess of 5,000 oe. is applied to the solid waveguide 8 along the zaxis 32 of the coordinate system 30. The direction of the magnetic field is parallel to and coincident with both the metal coated top surface 20' and the non-metallized bottom surface 36. It has been found that with this arrangement of microwave signal, magnetic field and solid state waveguide 8, the microwave energy can propagate in the direction of the vector 28 along the top or coated surface 20 of the solid state Waveguide 8 within the solid state material 14. As the strength of the magnetic field is increased, the attenuation of the microwave signal through the solid state waveguide 8 is decreased. If the magnetic field strength is increased from approximately 5,000 oe. to 14,000 oe., the microwave signal, with an input power of 2 milliwatts, will propagate with an output power that varies from approximately .0O 7S milliwatt to .075 milliwatt accordingly.

If either the direction of the magnetic field or the direction of the propagated microwave energy is reversed from that described above in connection with FIG. 1, microwave energy willtend to propagate along the non-metallized bottom surface 36 of the solid state waveguide 8. The resulting signal, in comparison to the microwave energy propagated along the top surface 20, is greatly attenuated. When, for example, the magnetic field is varied from approximately 5,000 oe. to 14,000 oe., the microwave signal propagated along the bottom surface 36 rises from a transmission of essentially zero power to approxi-.

mately .0005 milliwatt, or about one-hundredth the power transmitted along the top surface 20. This nonreciprocal quality permits the use of this solid state Waveguide 8 as an isolator. The use of the absorbing material 38 enhances the attenuation of the radio frequency energy.

Another example of the configuration shown in FIG. 1 with improved performancewas constructed of n-type InSb of smaller dimensions, for example, having end surfaces 24 and 26 of approximately 1 millimeter height by 8 millimeters width, with the distance between the end surfaces 0.85 mm, A carbon power-silicone grease mixture was used to cover the lower surface 36 to more effectively absorb the microwave power in the reverse direction. For applied magnetic fields between 2,000 cc. and 7,000 oe., the attenuation of the signal with the magnetic field in the z-direction 32 decreased from 22 db to 3 db, while for the reversed direction of field, the attenuation dropped into a solid state waveguide propagates therethrough because of the presence of free charge carriers. The free charge carriers are acted upon by the electric field of the microwave energy and the applied DC. magnetic field. This may be more fully understood by a consideration of solid state material with free charge carriers of electrons. The electrons of the solid state material, considered in the example discussed in connection with FIG. 1, exhibit a high degree of mobility (hence the reference to n-type, InSb). These electrons move at a velocity in response to an RF electric field ofan applied microwave energy. As these electrons move through a DC. magnetic field, they are subjected to a force which tends to propel them in a direction which can be described by a vector. This vector is the resultant of a cross-product of the direction of velocity caused by the RF electric field and the direction of the DC. magnetic field. If the magnetic field is great enough, the electrons will group at regular intervals. This grouping can be referred to as Space Charge.

With respect to such solid state material as has been indicated, the magnetic field is perpendicular to the electric field component in the direction of propagation of microwave energy. Space charge will be found at regular interval-s in the direction of the propagation of microwave energy. If parallel surfaces (which can be substantially parallel to the direction of propagation of the microwave energy and parallel to the direction of the magnetic field) are metal coated, a potential electric field will be set up between the surfaces and the space charge. It is believed that this electric field will add to the electric field component of the inserted microwave energy along one metal surface and subtract along a parallel metal coated surface. This conclusion can be drawn from the article by R. Hirota, Journal of the Physical Society of Japan, vol. 19, No. 7, pp. 1l301134,'July 196-4. The article by Dr. Hirota indicates that the microwave energy is propagated through the solid state material in a form. of a modified TE wave. Such a modified TE wave will occur if the inserted microwave energy is in a TE or TM mode. The surface along which the microwave energy will propagate is believed to be described by a vector pointing in the direction of the surface. The vector is the resultant of a cross-product of the direction of propagation of the rfinilcdrowave energy and the direction of the DO. magnetic Thus, assuming a solid state Waveguide having substantially parallel, metal coated surfaces, microwave en ergy propagated in one direction through the waveguide can be made to propagate along one of the metallized surfaces and not the other metallized surface. Microwave energy propagated in a reverse or different direction through the waveguide can be made to propagate along the other or second metallized surface and not the one metallized surface. An application is shown in the embodiment of FIG. 1, where microwave energy can bev made to propagate in one direction along the top, metallized surface 2ti.'By leaving the bottom surface 36 nonmetallized, microwave energy coupled tothe Waveguide 8 in the reverse direction is attenuated, providing an iso- The isolator shown in FIG. 1 may be converted to a microwave modulator and switch by applying a small, varying magnetic field directionally in the y-z (34-32) plane of the coordinate system 3%). Sharp variations in the transmitting power take place. With reference to the particular example discussed in connection with FIG. 1, the

transmitting power can be reduced by one-half by directing the magnetic field initially directed along the z-axis 32 at an angle of only 1 above the z-axis 32 in the y-z (34-32) plane. This same dependence on the angle of the magnetic field in the y-z (34-32) plane may be accomplished by the introduction of a separate modulatory magnetic field coincident with the y-axis 34.

It has been found both experimentally and theoretically that not only the attenuation but also the phase of a wave propagated in a structure, as shown in FIG. 1, is a function of the magnetic field. The detailed theoretical description of such dependence on the magnetic field is given in the paper of I-Iirota cited above. In actual experiments at K-band, phase shifts of as much as 60 degrees have been observed when the magnetic field was changed from 6,000 to 13,000 gauss. It follows that the structure of FIG. 1 can by controlling the magnitude of the applied magnetic field produce a desired phase shift of an applied microwave.

A further device which may be suitably used for a phase shifter 40 is shown schematically in FIG. 2. A solid state matter 14, which may be either a semimetal or semiconductor, has a substantially rectangular shape 42. Surmounting the rectangular shape 42 is a substantially rectangular shaped protuberance 44. The exterior top surface of the semiconductive material comprises the top surface 46 of the larger rectangular portion and the parallel sides 48 and top surface 50 of the rectangular protuberance 44. The bottom suface 52 is covered with a thin sheet or coat of conductive metal 22. The top surfaces 46 and 50 of the phase shifter 40 have a thin metal coat 22. The side surfaces 48, which are transverse to the plane of the top surface 46, are covered with a thin coat of metal 22. Thus, a continuously metal coated top surface is formed.

Microwave energy will tend to propagate along the bottom suface 52 (from right to left in FIG. 2 of the phase shifter 40 upon insertion from the right side (as indicated by an arrow 54). Such propagation will take place, if in accordance with the previously explained method of propagation, a magnetic field may be imagined to be parallel to and coincident with both the top surfaces 46, 48, and 5t? and bottom surface 52 of the phase shifter 40 and perpendicular to the direction of propagation of the microwave energy. In FIG. 2 the direction of the magnetic field is represented by a circle with an x drawn therein 56, which indicates a magnetic field entering perpendicular to the surface of FIG. 2. Microwave energ inserted from the left of FIG. 2. (as indicated by the arrow 58) will propagate along the top surfaces 46, 48 and 50 of the phase shifter 40. Such propagation will occur if a substantial part of the electric field component of the microwave energy is perpendicular to the magnetic field. As the parallel side surfaces 48 of the rectangular protrusion 44 are increased in length, or as the magnetic field is decreased, the phase shift of the propagated microwave signal will be increased. If the side surfaces 43 of the rectangular protuberance 44 provide a phase shift of 180, the resulting device is called a gyrator.

FIG. 3 is a schematic representation of a duplexer 60 constructed so that it may operate in accordance with the principles of propagating microwave energy along the metaI coated surfaces 22 of a solid state waveguide. The duplexer 60 is T shaped having a stem 62 and a crossmember 6 4 of solid state material 14. The lower surface 66 of cross-member 64 and a pair of parallel side surfaces 68 of the stem 62 form two L-shaped surfaces 70 and 72. The L-shaped surfaces 70 and 72 and the top surface 74 of the cross-member 64 are coated with a thin sheet of conductive substance 22 which can be metal. A microwave signal, introduced into the stem 62 of the duplexer 60 may be made to propagate along one or the other of the L-shaped surfaces 70 or 72 by applying a magnetic field parallel to and coincident with the L-shaped surfaces 70 and 72 in a proper direction. For example,

if, in accordance with principles discussed in connection with FIGS. 1 and 2, a magnetic field is directed perpendicularly into the surface of FIG. 3 (as indicated by a circle with an x inscribed therein 56), the microwave energy will propagate along the left L-shaped surface 72 in FIG. 3.

In a similar manner the channeling of microwave signals through chosen paths of a duplexer 60, in FIG. 3, may be employed in a circulator '78 shown in FIG. 4. Thus, the L-shaped surfaces (89, 82, 84, 86) of the circulator 78 may be employed to direct a microwave signal. The schematic representation of a circulator in FIG. 4 is that of rectangular cross-members 88 and 90 of solid state material 14. The rectangular cross-members 88 and 90 of solid state material 14, form four L-shaped surfaces: 80, 82, 84 and 86, which are covered with a thin coat of conductive substance 22 which can be metal. Application of a magnetic field in the proper direction causes a microwave signal inserted at one of the members to propagate along an L-shaped surface within the solid state material 14. Thus, in accordance with the principles discussed with respect to FIGS. 1 and 2, the magnetic field is applied parallel to and coincident with the L-shaped surfaces 80, 82, 84, and 86; perpendicular to the direction of propagation; and perpendicularly into the surface of FIG. 4 (as indicated by a circle with an x drawn therein 56). Microwave energy will propagate along the L-shaped surfaces in the direction indicated by the arrows 92, 94, 26, or 98. In the embodiments of FIGS. 3 and 4, abrupt intersecting angles for adjoining surfaces have been shown. Instead of L-shaped surfaces, the surface intersections can be gradual or shaped as desired. For example, the ci-rculator of FIG. 4 may be formed with four sides, each of which is U-shaped.

FIG. 5 is a schematic representation of a means for switching and otherwise controlling microwave energy propagated through solid state waveguide. A solid state waveguide 8 constructed of a semi-conductor or semisolid substance 14 having a rectangular shape with a metal coating 22 separated from its top surface 20 by a layer 104 of suitable insulating material is inserted be tween two hollow waveguides 10 and 12 in a manner similar to that shown in FIG. 1. In FIG 5, the two side surfaces 16 and 18 of the solid state waveguide 8 are not coated with a conductive substance. Connections 160 and 102 capable of carrying current supplied by a suitable source, not shown, via terminals 106, 108 are affixed to the side surfaces 16 and 18, respectively, of the waveguide 8. An insulating layer 104 on the surface 20 is used to reduce the DC. current flow through the metal coating 22. Alternately, the metal coating may contain narrow breaks perpendicular to the current flow direction between side surfaces 16, 18.

In accordance with the discussion directed to FIG. 1, a microwave signal in the TE mode directed from the right side of FIG. 5 (indicated by the vector 28 on the x-axis of a coordinate system 30) will propagate through the solid state waveguide 8 when a magnetic field (indicated by the vector 32 drawn on the z-axis of the coordinate system) is directed perpendicularly to the direction of propagation 28 of the microwave energy and parallel to and coincident with the top surface 20. The resulting grouping of space charge as discussed above can be disturbed by the introduction of energy transverse to the direction of propagation 28 of the microwave energy and parallel to the surface 20 of the waveguide 8. Such disturbance can be used to control or modulate the propagation of the microwave energy. The greater the disturbance of the RF space charge fields, the greater the absorption of microwave energy.

The disturbance may be caused by impact ionization, light stimulation or current. In FIG. 5 the means used to disturb the space charge fields is current passed through the affixed connections and 102.

Another means of controllably disturbing the space charge fields is to introduce a mild magnetic field in a direction parallel to the direction of propagation 28 of the microwave energy. Such a field, when in the same direction as that of microwave energy flow, causes a concentration of the electron and hole charge carriers at the surface where the microwave energy is propagating, resulting in increased absorption. In FIG. the means used to so disturb the space charge fields with a magnetic field is provided by a coil of current carrying wire 110 wrapped about the waveguide 8. A suitable source, not shown, is connected to the coil 110 via terminals 112, 114. This method of varying the magnetic field should be used concurrently with the energy injection method as discussed in connection with the current carrying connections 100 and 102.

What is claimed is:

1. A waveguide comprising:

(a) a body constructed of a material having at least one substantially broad planar surface, said material having free charge carriers,

(b) a thin conductive coating affixed to and coextensive with said planar surface to form with said body said waveguide,

(c) means for coupling microwave energy to said body in a direction substantially parallel to said coated surface, a portion of the electric field component of said microwave energy being substantially perpendicular to said coated surface of said body, and

(d) means for applying a magnetic field to said body at least part of which is directed parallel to and coincident with said coated surface and perpendicular to the direction of said microwave energy to cause said microwave energy to propagate along said coated planar surface within said body.

2. A waveguide comprising:

(a) a body constructed of material having free charge carriers therein and at least twosubstantially broad parallel planar surfaces,

(b) a thin conductive coating in contact and coextensive with at least one of said surfaces to form solely with said body said waveguide,

(0) means for coupling microwave energy to said body in a direction parallel to said surfaces, a portion of the electric field component of said microwave energy being substantially perpendicular to said surfaces of said body, and

(d) means for applying a magnetic field to said body at least part of which is directed parallel to and coincident with said surfaces and perpendicular to the direction of said microwave energy so that the cross-product of said direction of said microwave energy and said direction of said magnetic field results in a vector directed toward said coated surface, whereby said microwave energy propagates along said coated surface and is attenuated at said other surface within said body.

3. A waveguide comprising:

(a) a body of material having free charge carriers and at least two substantially broad parallel planar surfaces,

(b) a thin conducting coating in contact and coextensive with each of said surfaces to form withsaid body said waveguide, the coating on one of said surfaces being separate from that on the other of said surfaces,

(c) means for coupling microwave energy to said body directed parallel to said surfaces, a portion of the electric field component of said microwave energy being substantially perpendicular to said surfaces of said waveguide, and

(d) means for applying a magnetic field to said body at least part of which is directed parallel to and coincident with said surfaces and perpendicular to the direction of said microwave energy to cause the cross-product of said direction of said microwave 0 energy and said direction of said magnetic field to result in a vector directed toward one of said coated surfaces, whereby said microwave energy tends to propagate along said one coated surface and is attenuated at said other coated surface.

4. A waveguide modulator comprising:

(a) a body of material having free charge carriers therein,

(b) a conductive coating afiixed to and coextensive with a broad planar surface of said body to form solely with said body said waveguide,

(c) means for coupling microwave energy to said body direct-ed parallel to said surface with a portion of the electric fieldcomponent of said microwave energy being substantially perpendicular to said surface,

(d) means for applying a first magnetic field to said body directed substantially parallel to and coincident with said surface and perpendicular to said direction of said microwave energy to cause said microwave energy topropagate only along said surface within said body, and

(e) means for applying a second magnetic field to said body directed substantially perpendicular to said surface with said second magnetic field being varied to modulate and control said microwave energy as it propagates within said body;

5. A waveguide comprising:

(a) a body of material having free charge carriers therein and at least one substantially broad planar surface,

(b) a thin conductive coating on and coextensive with said surface to form with said body said waveguide,

(c) means for coupling microwave energy to said body in a direction parallel to said surface, a portion of the electric field component of said microwave energy being substantially perpendicular to said surface,

(d) means for applying a magnetic field to said body directed substantially parallel to and coincident with said surface and perpendicular to said direction of said microwave energy to cause said microwave energy to propagate along said surface within said body, and

(e) means for controlling the ambient temperature of said body in a manner to reduce the attenuation of said microwave energy as it propagates through said body.

6. An isolator comprising:

(a) a rectangular shaped body of material having free charge carriers and first and second surfaces at opposite sides of said body,

(b) .a thin conductive coating on said first surface and on at least one side surface of said body adjacent to said first surface to form with said body a waveguide,

(42) means for coupling a first microwave signal to said body in a direction substantially parallel to said first and second surfaces with a portion of the electric field component of the microwave signal being substantially perpendicular to said first and second surfaces,

((1) means for applying a magnetic field to said body directed substantially parallel to and coincident with said first and second surfaces and perpendicular to said direction of said microwave energy to cause the cross-product of said direction of said microwave signal and said direction of said magnetic field to result in a vector directed toward said first coated surface, whereby said microwave signal propagates along said first coated surface within said body, and

(e) means for coupling a second microwave signal to said body in an opposite direction to said direction of said first microwave signal so that the cross-product of said direction of said second microwave signal and said direction of said magnetic field results in a vector directed toward said second uncoated surface and the attenuation of said second microwave signal at said second surface.

7. A waveguide isolator comprising:

(a) a rectangularly shaped body of semiconductor material of one type of conductivity having free charge carriers therein,

(b) a coating of a conductive metal on the top and two parallel side surfaces of said body, said side surfaces being adjacent to said top surface,

() a coating of microwave energy absorbing material on the bottom surface of said body opposite to said top surface,

(d) means for coupling a first microwave signal to on uncoated end of said body directed parallel to said top and side surfaces with a portion of the electric field component of said first microwave signal being substantially perpendicular to said top surface,

(e) means for applying a magnetic field to said body directed substantially parallel to and coincident with said top and bottom surfaces and perpendicular to said side surfaces, said magnetic field being applied perpendicular to said direction of said first microwave signal to cause said first microwave signal to propagate along said top surface within said body, and

(f) means for coupling a second microwave signal to the other uncoated end of said body directed opposite to said direction of said first microwave signal so that the cross-product of said direction of said second microwave signal and said direction of magnetic field result in a vector directed toward said bottom surface and the attenuation of said second signal at said second surface.

8. A phase shifter comprising:

(a) a body of material having free charge carrierst therein, said body being of a rectangular shape with a rectangular protuberance on the top surface of said body,

(b) a conductive coating on said top surface including said protuberance so that a continuous coating covers said top surface and said protuberance,

(c) a conductive coating on the bottom surface of said body opposite to said top surface,

(d) means for coupling a first microwave signal to said body directed parallel to said top and bottom surfaces with a-p ortion of the electric field component of the microwave signal being substantially perpendicular to said surfaces,

(e) means for applying a magnetic field to said body directed substantially parallel to and coincident with said surfaces and perpendicular to said direction of propagation of said first microwave signal such that the cross-product of said direction of said first microwave energy and said direction if said magnetic field results in a vector directed toward said top conductive coated surface, whereby said first microwave signal propagates along said top surface within said body and is subjected to a phase shift determined by the over-all length of said top surface including said protuberance, and

(f) means for coupling a second microwave signal to said body in an opposite direction to the direction of said first microwave signal to cause the cross-product of said direction of said second microwave signal and said direction of said magnetic field to result in a vector directed toward said bottom surface, whereby said second microwave signal propagates within said body above said bottom surface and is subjected to a different phase shift than is said first signal due to the difference in over-all length between that of said bottom surface and that of said top surface including said protuberance.

9. A waveguide duplexer comprising:

(a) a body of material having free charge carriers therein, said body having the shape of a T so that 10 a pair of parallel surfaces of the stem of said T form with the bottom surface of the cross-member of said T a pair of generally L-shaped surfaces,

(b) a conductive coating on each of said L-shaped surfaces with the coating on one of said L-shaped surfaces being separate from the coating on the other,

(c) means for coupling a microwave signal to said stem of said body in a direction parallel to said conductive coated surfaces of said stem with a portion of the electric field component of said signal being substantially perpendicular to said conductive coated surfaces, and

((1) means for applying a DC. magnetic field of reversible direction to said body parallel to and coincident with said L-shaped surfaces and perpendicular to said direction of said microwave signal so that when said field is in one direction perpendicular to said direction of said signal the cross-product of said direction of said microwave energy and said direction of said magnetic field results in a vector directed toward a first of said L-shaped surfaces causing said microwave signal to propagate along said first L-shaped surface within said body, the cross-product of said direction of said microwave signal and said direction of said magnetic field upon field being applied in the opposite direction to said one direction perpendicular to the direction of said signal resulting in a vector directed toward said second L-shaped surface causing said microwave signal to propagate within said body along said second L-shaped surface.

10. A waveguide device comprising:

(a) a body of material having free charge carriers therein, said body being formed with a plurality of surface areas extending radially about said body to which microwave signal energy can be applied,

(b) a conductive coating on and coextensive with that part of said surfaces of said body located between each of said radially extending surface areas and the next adjacent one of said radially extending surface areas with each coated surface between adjacent ones of said radially extending surface areas being separate from every other coated surface of said body,

(c) means for coupling a microwave signal to one of said surface areas with a portion of the electric field component of said signal being substantially perpendicular to a given coated surface having one end at said one surface area, and

(d) means for applying a magnetic field to said body in a direction substantially parallel to and coincident with said coated surfaces of said body and perpendicular to said direction of said microwave signal causing the cross-product of said direction of propagation of said microwave signal and said direction of said magnetic field to result in a vector directed toward said given coated surface, whereby said microwave signal propagates along said given coated adjacent radially extending surface within said body and is derivable from the surface area at the end of said given coating opposite to said one end.

11. A waveguide circulator comprising:

(a) a body of material in the shape of a cross having four arms, the arms of said cross forming with one another L-shaped surfaces, the planar portions of each L-shaped surface being parallel to similar portions of another of the L-shaped surfaces formed by said arms, said material having free charge carriers therein,

(b) a conductive coating on each of said L-shaped surfaces so that the respective L-shaped coated surfaces are separate from one another,

(c)imeans for coupling microwave energy to at least one of said arms with a portion of the electric field component of said signal being substantially perpendicular to said coated surfaces, and

ill

(d) means for applying a magnetic field to said body with at least part of said magnetic field being directed parallel to and coincident with said L-shaped surfaces and perpendicular to said direction of said microwave signal so that the cross-product of said direction of said microwave signal and said direction of said magnetic field results in a vector directed toward one of said coated L-shaped surfaces, whereby said microwave signal propagates along said one L-s'haped surface within said body.

12. A waveguide device comprising:

(a) a body of material having free charge carriers therein,

(b) a conductive coating afiiXed near and contiguous with a surface of said body,

(c) means for propagating microwave energy into said body directed parallel to said surface with a portion of the electric field component of said microwave energy being substantially perpendicular to said surface,

((1) means for applying a magnetic field to said body directed substantially parallel to and coincident with said surface and perpendicular to the direction of propagation of said microwave energy, whereby said microwave energy propagates along said surface within said body by the grouping of said free charge carriers to establish space charge fields at intervals within said body,

(e) means for varying said grouping of said free charge carriers, and

(f) means for applying a second magnetic field parallel to said direction of said microwave energy, whereby the propagation of said microwave energy within said body is determined by said varying means and said second magnetic field applying means.

13. A waveguide device comprising:

(a) a body of semiconductor material having free charge carriers therein and formed in a rectangular shape,

(b) a metallic conductive coating affixed to and insulated from a surface of said body,

(c) means for propagating microwave energy into said body directed parallel to said coated surface with a portion of the electric field componentof said microwave energy being substantially perpendicularto said coated surface,

(d) means for applying a magnetic field to said body directed substantially parallel to and coincident with said coated surface and perpendicular to said direction of propagation of said microwave energy causing the cross-product of said direction of propagation of said microwave energy and said direction of the magnetic field to result in a vector directed toward said coated surface, whereby said microwave energy propagates along said coated surface within said body by grouping said free charge carriers at intervals within said body, and

(e) means for applying an electric field to said body transverse to said direction of propagation of said microwave energy and parallel to said direction of said magnetic field to vary said groupings of said free charge carriers.

14. A waveguide device comprising:

(a) a body of semiconductive material having free charge carriers therein and formed in a rectangular shape,

(b) a conductive coating afiixed to and insulated from a surface of said body,

() means for propagating microwave energy into said body directed parallel to said coated surface with a portion of electric field component of said microwave energy being substantially perpendicular to said coated surfaces,

((1) means for applying a magnetic field to said body directed substantially parallel to and coincident with said coated surface and perpendicular to said direction of propagation of said microwave energy such that the cross-product of said direction of propagation of said microwave energy and said direction of said magnetic field results in a vector directed toward said coated surface, whereby said microwave energy propagates along said coated surface within said body by the grouping of said free charge carriers at intervals within said body,

(e) means for applying an electric field to said body transverse to said direction of propagation of said microwave energy and parallel to said direction of said magnetic field in a manner to vary the concentration of said grouping of said charge carriers,

(f) means for applying a second magnetic field to said body in a direction substantially parallel to said direction of said microwave energy and perpendicular to said magnetic field, and

(g) whereby the propagation of said microwave energy within said body can be determined by said electric field and said second magnetic field applying means.

15. A waveguide device comprising:

(a) a semiconductor body having free charge carriers and formed in a rectangularshape,

(b) a conductive coating afiixed to and insulated from a first top surface of said semiconductor,

(c) means for propagating a microwave signal into said body directed parallel to said top surface and to second and third side surfaces of said body with a portion of the electric field component of said microwave signal being substantially perpendicular to said top surface,

(d) means for applying D.C. magnetic field to said,

body substantially parallel to and coincident with said top surface, perpendicular to said side surfaces and perpendicular to said direction of said microwave signal suchthat the cross-product of said direction of propagation of said microwave energy and said direction of said magnetic field results in a vector directed toward said top surface, whereby said microwave signal propagates along said top surface within said body by the grouping of said charge carriers at regular intervals within said body,

(e) a first electrical connection made to said second side surface,

(f) a second electrical connection made to said third side surface, and

(g) means for applying an electric field to said body via said connection with said electric field being applied transverse to said direction of said microwave signal and parallel to said direction of said magnetic field in a manner to vary the concentration of said charge carriers within said groupings.

16. A waveguide device comprising:

(a) a semiconductor bod yhaving free charge carriers therein and formed in a rectangular shape,

(b) a conductive coating on but insulated from a first top surface of said body,

(c) means for propagating a microwave signal into said body directed parallel to said top surface and to second and third side surfaces of said body with a portion of the electric field component of said microwave signal being substantially perpendicular to said top surface,

(d) means for applying a first magnet field to said body substantially parallel to and coincident with said top surface, perpendicular to said side surfaces, and perpendicular to said direction of said microwave signal causing the cross-product of said direction of propagation of said microwave energy and said direction of said first magnetic field to result in a vector directed toward said top surface, whereby said microwave signal propagates along said coated surface within said body by the grouping of said charge carriers at regular intervals within said body,

(e) a first electrical connection made to said second side surface,

(f) a second electrical connection made to said third surface,

g) means including said connections for applying an electric field to said body transverse to said direction of said microwave signal and parallel to said direction of said magnetic field in a manner to vary the concentration of said grouping of said free charge carriers, and

(h) means for applying a second magnetic field substantially parallel to said direction of said microwave energy and perpendicular to said first magnetic field and said electric field to control the propagation of said microwave signal within said body.

17. In combination:

a body of material having free charge carriers therein,

means for coupling microwave energy into said body directed substantially parallel to a surface of said body, a portion of the electric field component of said microwave energy being substantially perpendicular to said surface,

means for causing said microwave energy to propagate along said surface within said body by the grouping of said free charge carriers at intervals within said body in the presence of a magnetic field applied to said body at least part of which is directed parallel to and coincident with said surface and perpendicular to said direction of said microwave energy, and

means for varying the concentration of said grouped charge carriers to control the propagation of said microwave energy within said body.

means including a thin conductive coating on said planar surface of said body for causing said microwave energy to propagate along said surface within said body in the presence of a magnetic field applied to said body at least part of which is directed aparallel to and coincident with said coated surface and perpendicular to said direction to said microwave energy.

18. In combination:

a body of material having free charge carriers theremeans for coupling microwave energy into said body and directed substantially parallel to a surface of said body, a portion of the electric field component of said microwave energy being substantially perpendicular to said surface, and

means for causing said microwave energy to propagate along said surface within said body in the presence of a magnetic field applied to said body at least part of which is directed parallel to and coincident with said surface and perpendicular to said direction of said microwave energy.

19. In combination:

a body of material having at least one substantially broad planar surface, said body having free charge carriers,

means for coupling microwave energy into said body in a direction substantially parallel to said planar surface, a portion of the electric field component of said microwave energy being substantially perpendicular to said planar surface of said body, and

References Cited The Institution of Electrical Engineers, Paper No.

3780 E. March 1962, p. 137-144.

Proc. IEE, vol. 10, No. 12, December 1963, pp.2177- 5 3 HERMAN KARL SAALBACH, Primary Examiner.

P. L. GENSLER, Assistant Examiner. 

18. IN COMBINATION: A BODY OF MATERIAL HAVING FREE CHARGE CARRIERS THEREIN, MEANS FOR COUPLING MICROWAVE ENERGY INTO SAID BODY AND DIRECTED SUBSTANTIALLY PARALLEL TO A SURFACE OF SAID BODY, A PORTION OF THE ELECTRIC FIELD COMPONENT OF SAID MICROWAVE ENERGY BEING SUBSTANTIALLY PERPENDICULAR TO SAID SURFACE, AND MEANS FOR CAUSING SAID MICROWAVE ENERGY TO PROPAGATE ALONG SAID SURFACE WITHIN SAID BODY IN THE PRESENCE OF A MAGNETIC FIELD APPLIED TO SAID BODY AT LEAST PART OF WHICH IS DIRECTED PARALLEL TO AND COINCIDENT WITH SAID SURFACE AND PERPENDICULAR TO SAID DIRECTION OF SAID MICROWAVE ENERGY. 